Combating interference is one of the most outstanding challenges in wireless communication networks, especially for cellular networks with frequency reuse one. This issue becomes even more significant in heterogeneous networks where lower power nodes (such as pico-cell and/or femto-cell) are deployed within a macro-cell's coverage. In this paper, the authors investigate interference coordination techniques in different scenarios. For homogeneous networks, they study single-cell multiuser MIMO for the purpose of intra-cell interference coordination and Coordinated Multi-Point (CoMP) transmission for the purpose of inter-cell interference mitigation. For multi-user MIMO systems, they will discuss multi-user MIMO proportional-fair scheduling as well as multi-user pre-coding schemes. For CoMP transmission, they will focus on CoMP joint transmission and discuss the situations where CoMP could provide performance gains over single-cell operations.